docs: def step1(self, pin):
          """First pairing step."""
          context = SRPContext(
              'Pair-Setup', str(pin),
              prime=constants.PRIME_3072,
              generator=constants.PRIME_3072_GEN,
              hash_func=hashlib.sha512)
          self._session = SRPClientSession(
              context, binascii.hexlify(self._auth_private).decode())